Thailand with 2 little kids in May

Other than that, you see plenty of Europeans around with small children and some sort of buggy/stroller/push chair.
Yeah, because only Europeans are dumb enough to use a push chair in Thailand.
There is a reason Thais won't use them.

Seriously, do you actually think a pushchair could be used on Bkk pavements, especially Sukhumvit where the OP was thinking of staying, or in the Ayutthaya ruins? Even Kanchanaburi would be a stretch.
The islands are just part of the OP's trip.

Many roads don't even have pavements, so you would be pushing the stroller in the street mixing it with the traffic. But, by all means tell someone that has never been to Thailand that it's just fine to use a buggy, especially a huge one like the mountain buggy which would be a very antisocial thing to use on Bkk streets where there is often just room for single file walking.

seen 2 guys in different wheelchair types here on Koh samui
And I've seen guys in wheelchairs in Pattaya. It's just limited to a few very small areas of Thailand.
BTW Samui is not the same as Phangan or Tao. It's far more developed for starters.

OP, seriously, if you want to take the boy, use one of those backpack things where you can carry the kid on your back.

Dont forget some see the glass as half empty others as the glass half full.
Assuming that is aimed at me, I've been coming to Thailand since the mid 1970s and lived here for years, so I know enough about Thailand to know the reality of life here. Nothing to do with half full/ empty.

As for where to stay in BKK, I stayed near Asoke (which is down Sukhumwit) with my 5 year old last year, because I find the Skytrain absolutely essential for getting around in the heat. I don't LOVE that area, and would prefer older parts of BKK, but it has a large selection of hotels with pools very near the Skytrain. She did not notice any of the nightlife, even though we were out at night, and so, outside of the seediest blocks, I wouldn't worry too much about that. Basically, it's a tradeoff of charm (other parts of BKK) and convenience. In May heat, your kids will need to spend a lot of time in the pool (as may you!).

I agree a stroller/pram/buggy would be useless, but I would have a baby carrier. The main risk to toddlers is all of the broken/uneven/holes in sidewalks and pavements.

Definitely do Ayutthaya.

Bring oral rehydration powders that your kids will drink, because in the heat they may need it.

Enjoy!

Many thanks to everyone who responded to my post!

@natalie2: good advice for Bangkok and where to stay there, getting around by boat sounds interesting, I will also look at some of the hotels near the river. Will look up the water levels at Erewan...

@friendly_checkingirl: great to know pre-booking is not essential. Makes things much more flexible. Thanks for the info on the coach/ferry to Koh Tao. But don't you think a night train sleeper would maybe be more comfortable and also fun? For taking Maite out snorkeling I thought of going out by kayak maybe. Will look into some of those Koh Tao bays.

@jjack thanks for your concern. Good to be careful.

@westwood: Re:babysitting, I was indeed thinking of something like that. We have a mountain buggy actually, however given the size I had not actually considered taking it with us. See below also please.

@thaibeachlovers: A lot of useful info in your answer, thank you.

Regarding taking the kids, well yeah they are part of our family so yes we do want to take them. We do not want to stop travelling just because there's kids in our lives now. It's true that until the age of 3 or 4 very little memories are lasting, however with that reasoning would you say there's no point in doing any activities, travels, experiences, any fun stuff with small kids? They can still have a great time doing them. You don't just travel for the memories, but also to enjoy the moments you are actually there. Also (fair enough if you don't agree) but I firmly believe exposing a small kid to different cultures and environments CAN have a positive impact on their development and character. BTW Leo (20 months old) can also walk.

Re:Climate: Oh... I am aware it will be rather hot everywhere. But really, is there not much notable difference between Chiang Mai and Kancha. or the islands? I need to re-check then...Chiang Mai would be back in the game if that's true. I thought I'd read Chiang Mai would be way worse and was therefore not really recommended around May. Hmmm...

@jenae: Thanks to you too. Hadn't heard of rehydration powders, will ask in my pharmacy.

We're still not decided on whether to take a foldable "umbrella-type" (as the French call it) stroller, or whether to leave it here. If anyone has any further input on that, please shout it out. I am aware it will be useless in most places as a way of "transport" (just most places or literally everywhere except for shopping malls in Bangkok?) - the use I see for it more than anything is rather to have somewhere to put your child when he wants to take a nap. However haven't made our mind up on whether that use justifies carrying it with and around with us. Tendency is currently to leave it here (and buy a cheap one in Bangkok that we can leave behind, if we do change our mind (and obviously only if they even exist there?)). Can you really use it nowhere at all? Or is it just that you can't use it everywhere? If it's useful on the islands but not in Kanchanaburi (or Chiang Mai :) and in some streets in Bangkok, I might still want to take it - if it's useful in less than 25% of the places I'd leave it here. What we are definitely planning on taking is a childcarrying backpack.

Charlie

TBH OP I think you need a bit of a reality check. I get your line of thought that kids are a part of life and familes do everything together and it's all a learning curve but you cannot have the same trip with little kids that you can without. To take a 4 year old snorkelling in a kayak has got to be one of the most irresponsible ideas I've heard in a long while.

The only time I can see that a buggy would be useful is if you wanted a nice evening meal and you had somewhere for your youngest to sleep whilst you enjoyed it. Having said that, transporting it to and from the restaurant more than wipes out any advantage it brings even if your eldest decided to play along and behave. Places that are buggy friendly in terms of landscape such as markets and malls, are packed with people who will be ready to kill you for the inconvenience you cause.

In reality, from a practical point of view you can't really venture far away from the comfort of your hotel, your kids will get cranky in the heat and humidity and there is nowhere to hide except the aircon of your hotel room. Yes you can drag them along all day but seriously if they're not having fun are you ?
I think doing less is possibly more in your case.

I went to Erewan Falls in May 2014 and there was a decent amount of water going over the falls. Fantastic place. Got there at 7:50 and were the first up the falls and had a waterfall (high up - maybe number five?) to ourselves for over an hour.

Well thanks, friendly checkingirl.

You know there are things called buoyancy aids, life jackets, inflatable armbands, even snorkeling vests, right?

Look, I haven't been there yet, I don't know how shallow the water is, nor whether there are any waves or currents, neither do I know the distance from shore to the reef... I was merely expressing an idea, nothing more nothing less. Of course I'll see whether this idea is realistic or not when we get there. With the necessary information it will be possible for me to judge whether taking my daughter out by kayak and let her have a look into Nemo's world is a safe thing to do or not. Do you really think I would put my daughter at risk of drowning?

Thinking about friends kids of that age when we had been on the beach it seemed that shallow water was the place to play in and to get dirty in the sand. Most kids preferred a pool over the sea as they don't like it when the salt water gets into their eyes. Same will be a problem with leaking masks or goggles - or the kid being hurt when the straps are too tight.
Personally for above reasons I think that shallow sandy beach without rocks or corals are likely better for kids and a pool can be a plus.
Maybe do the snorkeling experiment on a beach you reach as a day/half day excursion.

Waterfalls always are a favourite for kids, doesn't matter really if it looks pretty or not, getting wet is the fun part.
The steam engines on display at the river kwai bridge might be fun for the kids, the train ride from Kanchanaburi to Nam Tok isn't too long and kids and adults like it going over the old viaduct along the cliff and river.

Dunno if the temples of Ayuttheya would be of much interest to the kids, after visiting temples in Bangkok?
Erawan Museum with its huge 3 headed elephant and going into its belly might make for a more interesting day trip, combined with ancient Siam/ancient city, sort of miniature Thailand with replicas from the entire country, tandem push bike riding around the compound might be fun.
Could add nearby Bang Pu pier with hundreds on seagulls zooming in right over the heads of the folks on the pier to be fed.
Have dinner at one of the ocean side restaurants and back to the city.
Skytrain to end of line and from there by taxi best way for a family I guess.

Hey, that must be a rare post where we agree on something, LOL.
I once saw a man pushing one of those antisocial side by side buggies through the stalls on Sukhumvit near Soi 5. He looked suitably embarrased and I'm certain there were more than a few "ready to kill him for the inconvenience he caused". Anyone familiar with the Sukhumvit stalls will know what I mean, barely enough room for single file pedestrians.

I agree 100% with your last paragraph.

Regarding taking the kids, well yeah they are part of our family so yes we do want to take them. We do not want to stop travelling just because there's kids in our lives now.
I was not suggesting that you not travel, more along the line of leaving the youngest with one of the grandparents etc. Take him and it all becomes about him, ergo, no one else will enjoy the trip.
At least the older child might remember something of the trip and can sit in a chair.
Be different if you were only going to one beach and staying there for the duration- lots of families with very young children do that succesfully.
Travelling around a lot in the heat and with the inevitable delays and problems- more like the 10th circle of hell.
But hey, what do I know- OTY.

Hot, yes, DAMN HOT. There might be a difference between Kanch and C M, islands, but you won't notice it. I had the fan on the other day, but it was just blowing super hot air, so I had to give in and use the AC.