The Canon 600D comes with a 77% silver award from dpreview which is a pretty high rating for such an "inexpensive" camera but once again, any savings you make in Thailand might be down to the VAT rate of your country.
VAT in Thailand stands at 7% so that is roughly the difference in the price you might pay at home. If you are unfortunate enough to come from the UK where VAT is a massive 20%, savings could be made, especially if you are able to get the VAT back when you leave the country.
The Canon Rebel T3i in the UK, in Thai Baht, is 28.650 compared to 29,500 in Thailand ! Knock off 2,065 for VAT and this brings the Thai price down to 27,435 Baht - a saving of 1,215 Baht or 25 UK pounds; hardly a massive saving.
The same camera from USA Amazon is 26,998 Baht, so even with the 7% VAT knocked off, the Canon EOS Rebel T3i is more expensive if purchased in Bangkok or Thailand.