The beer there is "meh", but that's not why you go to Thailand. It's the food, people and other activities.
I lived in Bangkok for a summer in 1990 and then came back in 2000. Two different trips, in 1990, there was one week where I didn't see the sun, I partied, with local Thais, all night. Then again I was 19, in Bangkok for the summer.
In 2000, I was with my ex-wife and it was a whole other type of trip; more site seeing. Not as much partying.
Place to visit:
Bangkok. Get a guidebook and visit the sites. Go out in the night market, gogo-bars, Patpong streets, temples, day markets, floating markets, etc
Chang-mai: must visit Do-su-teep temple, old city and get a suit made
Koh Samui or Koh Panaga are cool beach islands in the south.
Pataya beach, I would avoid