Help! I'm not having fun in Thailand

Take a trip to Luang Prabang on the river with the slow boat. You will have a lot of time to socialize on the boat. Then on to Vientiane and maybe Pakse. Dont try Chiang Rai and smaller places as the backpacker scene is more stretched out and people are more likely to be an a 'scheduled mission.' If nothing works, go south to the beaches preferably Andaman coast. Watch your budget.
There are also lots of backpackers in Siem Reap and Sihanoukville in Cambodia. Yet, keep in mind it is low season. Prices in SHV are way below the Andaman coast.

Never been to Thailand, so cannot give advice on the specific area, but I see Mike_asia did that.

However, i have backpacked a lot solo female in my twenties. Sometimes a place just does not agree with you. Maybe it's your state of mind at the particular moment, maybe it's just not the place for you, but regardless, the advantage of travelling independently is that you can just move on if this happen.

Hope you find what you are looking for again.

Easy "solution" is to change hostel...move to a busy place. If you look around,or online, you will find the most popular places.

Second. ..go to the more touristy restaurants, bars and start talking to people.

Other possibility is as above. ..change city.

Two weeks ago during Songkran there were tons of travellers here, but after the festival it always goes pretty quiet. Add to that the current heat wave with 40C/105F almost every day plus the seasonal haze, not the best time to be up north. But as already suggested first thing might be change to another guesthouse with more of a social vibe. Also look at doing some kind of group-based activity like a Thai cooking course.

Agree with all of the above...switch hotels........ and it is rediculously hot right now here... Was out by the Grand Canyon today and it's pretty quiet..Have you tried that.. Not sure if you like renting a bike, but driving throught the hills can be fun and always some cool scenery...

To my mind, that is part of the solo-travel cycle: moments of loneliness and "what am I doing wrong?" Looking back on a few decades of traveling, getting PAST those moments is a big part of my sense of confidence as a traveler and person. In general, what helped me get beyond them was to dive IN to the local culture in some way rather than hold it at an observer's distance. I had to take some risk, like really trying out my language skills when I thought they wouldn't work, or going down some dark market alley that I wasn't really sure welcomed me, or getting off the bus in some town I wasn't at ALL sure was going to work. And then usually, with risk would come gain -- a moment, an experience, a connection.

As for meeting other travelers, that's often just luck of the draw of where you are at that moment. Change GHs and your mood may cheer up remarkably. I remember doing that in CM once -- I think I didn't realize how much the indifferent staff at my GH were dragging down my mood until I switched to a new one, and I was SO much cheerier! And the one thing about group activities is they can be a wonderful way to meet people, and then go out for drinks another night, etc.

As for what else to do in CM, you mihgt be sticking to too narrow a slice of the city if you are mostly seeing the tour agencies. I would definitely explore the back streets, meditate a bit at a wat, and get away from the moat to observe a little more local life. That is, when you aren't hiding out from the awful heat of this time of year! Oh, and Friday is the Shan morning market ---- almost every week I daydream about being there and having Shan tofu for breakfast!

Change hotels..Go wash the elephants.Cooking class.You will meet people and run into them later And they might introduce you to more travelers.
I was by myself for 3-4 days,walked into Mad Dog Pizza,(Moon Muang Road,around Soi 2)and was made to feel right at home.4-5 PM,just walk in and say hi..An usa woman,23yo,hangs there on a Friday after work.Be friendly and they will embrace you.
PM me the results if you go.
Tell them "Glenn sent you."

Tell them "Glenn sent you."

Luggage???

I can agree with much of what Jenae wrote above in his/her excellent post.
Sometimes solo travel can be a pretty desolate experience, especially if you are naturally introverted, sitting alone while people all around seem to be having a wild time. I'd say avoid the ghettos like the plague as they can be even more isolating.

I'll put in a shout for a former LPTT favourite in Bangkok.

The Suk 11 Hostel (on Sukhumwit soi 11)used to be a very popular place for travellers and was once a great place to socialise, where travellers would actually sit and chat in the lobby/common area downstairs but since drinking and smoking in that area were banned and the former manager (once a regular poster here)left his full time duties to other less 'traveller friendly' family members, the place isn't the social hub it used to be. I'd even pop in there for a few (cheap) hours when I was living and working in BKK.
The clientèle was mainly backpackers in town for a few days looking to be away from the tourist trap backpacker enclaves in Khao San while not too keen on the nearby 'seedy' side of BKK's night life.
Finding themselves thrown together in the lobby/common area with like minded travellers, it was natural that people would get chatting, pop to the nearby 7-11 for cheap drinks, gravitate to the (now moved) pub next door or down to Cheap Charlie's bar a minute's walk away, and it wouldn't be long until a convivial atmosphere would abound. There was never a cliquey feel to the place either as such was the layout that once seated with a beer, you would find yourself drawn into things.
That said, there always seems to be little knots of backpacker types huddling around a table from Suk11 at Cheap Charlie's most nights so that could be an option for you to consider if you're heading back to Bangkok.
The place is still spotless, full of pleasant corners and a very good deal for that part of town close to transport links to all parts away, if Sukhumwit gets a bit much.