This trip happened when I was studying in INSEAD, Singapore earlier this year. (It's a 4 month exchange program) The flight from Singapore to Bangkok was dirt cheap and we stayed in hostel which cost like nothing. We tried different sorts of street food and took tuk tuk or public transportation. The trip didn't cost much and the experience was amazing.
Here's the list I would recommend you to try in Bangkok:
I don't recommend transgender show because I'm not into that and I watched it when I was a child. (I've traveled to Thailand several times.)
I also have to put something straight: there are lots of scams in Bangkok. TONS! Taxi drivers, tuk tuk drivers, random people on the street, travel agency, jewelry store, hospital... That really pissed me off after a rough day of being scammed. Most people are nice and it's safe in general. Just do some research on google (such as *tuk tuk / jewelry / scam*) and you still can have fun in the trip.
Definitely take a train to Ayutthaya! The package offered in travel agency is overpriced and they will tell you it's impossible to rent a motorbike there. (I asked them why and they couldn't answer.....)
I would recommend renting motorbike because it's pretty hot there. I often rode motorbike when I was in Taiwan so it was lots of fun for me!
Cooking class was lots of fun! The teacher was funny and explained every ingredient patiently. I'm not gonna lie: the dishes I made that day were so delicious! But I never try to make it by myself afterwards haha. (They also provided the printed recipe.)
Silom Thai Cooking School @ Bangkok
Floating markets near Bangkok: http://www.bangkok.com/shopping-market/floating-markets.htm
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