http://www.jimmys-adventures.net/trekking-northern-thailand/

Southern or Northern Thailand?
We are going to Thailand with my husband for 9 days at the end of february.
We are not sure whether to head for the beach or chang mai for jungle trekking.
We haven’t got a massive budget and also we live in Greece so beautiful beaches is not a novelty..
Please help with suggestions!
If you read your question, I think you will find the answer there – go north – chiang mai, chiang rai – if you are adventurous you can get to some out of the way places – if not, plenty of daytrips from there… also CM & CR you can stay for much much cheaper – the south is very touristy and they tend to get more expensive.
The north has more backpackers but you can find very decent small guesthouses for 10 euros a night – even less – in CM, I stay in a place for that price – in CR about 7 euros – I can afford more, but these placesare just fine -
Hill Tribe Trek, Northern Thailand