Hmm average is difficult ...depends where I go. I'm a budget traveler unlike most folk on this forum I think. Under 20000B would be my typical budget for a 2 week break in Thailand on a nice quiet beach on a relatively un-touristed island ....Ko Phayam for example ...including food, accommodation and transport to and from BKK.

Return fares for 2 (2nd class train fan sleeper)...............................1800
Return fares for 2 ferry .................................................. ................600
Beach front bungalow for two 12 nights @300/night .....................3600
Food and beer for 2................................................. ......approx 10,000
Extras .................................................. .......................................2000

Total............................................. .............................................18000