Might go to Thailand for 16 days in march/April

I'm thinking @ going to Thailand for 2 weeks in the end of march into the beginning of april.
We have a friend who lives in Bangkok, but would like other peoples advice on good things to do that are not that far from bangkok (willing to do a days travel but that is the most) I like trekking, temples, and great beaches
thanks alot jimy

Jimy,
One place you may want to visit is Kanchanaburi. River Kwai, trekking, rafting. Worth a look.

a coach jourrey to Krabi or phuket for the beaches.

we got flights from BKK to Krabi for about £45 each. then a minibus to Phuket for about £12, then another plane from phuket to BKK for about £35-40.

BKK is great but if you're gonna thailand you really should see the beaches/islands they are awesome.

Trekking, temples and great beaches - not far from Bangkok (willing to do a days traval at most)

A one day trekking trip from Bkk? Rise nice and early and perhaps you could try out Khao Yai in Korat province or, as said already, Kanchanaburi.

Temples? Well, howabout Bangkok's very own Temple of the Emerald Buddha, Wat Poh, Wat Benjamaborphit

Great beaches one day trip from Bkk? Rise nice and early and perhaps try out Rayong or Hua Hin/Cha-am.

Jimy,
A nice beach option that is only a few hours away from BKK is Hua Hin. Worth a look.