Nervous first time Thailand traveller!

In Bkk stay near but not on Khao San Rd.

In Chiang Mai stay in the Old City in the Chiang Mai Gate / Thapae Gate area. There is an only women place there if you don't feel safe with men around.

Exploring Islands usually refers to the Gulf Coast with Samui, Phangan and Tao, but plenty islands on the Andaman side too. I wouldn't stay on Phuket though. Try Krabi town as a base- cheap places to stay at there.

No need to book ahead in November. One of you stays with the bags while the other wanders around looking for a place.

Yes, Thailand is a dangerous place, but don't leave your brain at immigration like so many. Don't accept food/ drink from strangers on buses/ trains/ bars, don't get blind drunk, don't use illegal drugs EVER in Thailand, don't wander off alone on dark beaches, don't assume other tourists are OK, and never go drinking with Thai men.
Also, use a good money belt and don't put anything valuable in a bag that's out of your sight.
If you have never driven a m'bike, Thailand is not the place to learn, but if you must hire one NEVER NEVER NEVER leave your passport as security, and NEVER NEVER NEVER hire a jet ski. It's a good idea to read up on scams in Thailand- just google.
Insurance is essential- a short stay in hospital could bankrupt you.

If you are cautious, you will probably be like millions of other tourists and never have a problem.

If you dont feel confident having one of you wander off and look for a place to stay, then maybe book ahead night in each place you're going to be in.
In Bangkok, we stay at a guest house on Soi Rambuttri, run by the same family since we first stayed there in 1998. A safe place but doesnt take bookings.
In CM, its always been Centerplace GH, not in old part but again its family run and safe.

Thank you for your help, it's really appreciated :-)

Thank you for the advice :-)

Do as #1 says.
Pack your common sense. Don't do things you would not do at home and you will have a great time.

Soi Rambuttri is an excellent street to stay on.It is real close to Khao San Road...But the real fun is on Rambuttri.half the street is kind of quiet and the other quite lively.
I stayed at /www.rambuttrivillage.com//--About 600B./night..They have a rooftop pool,excellant rooms,hot water,and great security.We felt safe on this road at even 2 AM

Opps!..Rambuttri Village is 900B now..Not a good deal...Try //newsiam.net//..click New Siam Info;you will have a choice of 3 hotels..New Siam 1;is basic,small rooms,with the option of TV,AC,and private bathroom....New Siam 2,have real nice rooms and a pool.New Siam 1 is a good choice to put your luggage down and look around for something better.Skip New Siam 3.
In this area,you will be real close to a water taxi,which you can take to China Town.Great street food here and throughout BKK.

I wouldn't worry about finding accommodation and transport, that's usually very easy. I have just spent a year in Thailand and didn't encounter any situations where I felt threatened. If you follow the good advice given above you should be fine. I'd just add that it's a good idea to understand what 'loss of face' means to Thais. If you get in any disputes with locals any understanding of this can prevent things from getting nasty.

Thanks for the advice :-) Soi Rambuttri seems like a safe and convenient place to stay!