Thailand. First time there, looking for suggestions.

Heading to Thailand in about 3 months with a friend for around 10 days, probably landing in Bangkok. Looking for suggestions on what to do there. Things I'd love to do:

• experience the nightlife
• see all the amazing beaches and islands (Phuket? Kho Samui?)
• ride an elephant
• markets
• jungles/temples

Not really interested in staying in a 5 star in a city, will be backpacking it.

What say you, reddit?