My understanding is that I am liable for tax on the sale of the condo, which is assessed on the full sale amount (not just the capital gain) after an allowance of 50% (10 years ownership).
i.e. Sale price 11,500,000
Deduction 5,750,000
Balance = 5,750,000
Divided by the 10 years of possession
Balance = 575,000

Therefore taxation at existing rates:-
1 to 150,000 = exempt
150,001 - 500,000 = 10% (35,000)
500,001 - 575,000 = 20% (15,000)
Total = 50,000
Multiply by 10 years of possession = 500,000Baht

Or at the proposed new tax rates:-
1 to 150,000 = exempt
150,001 - 300,000 = 5% (7,500)
300,001 - 500,000 = 10% (20,000)
500,001 - 575,000 = 15% (11,250)
Total = 38,750
Multiply by 10 years of possession = 387,500Baht

Now the questions!
First, is my understanding (and maths!) above correct?
I heard somewhere that if the condo being sold has been your only residence, and the funds are being used to purchase another property in Thailand for your own use, the proceeds may be tax exempt. Can anybody confirm or shed any further light on this?
Furthermore, if there is some provision for this, does it apply to purchases of leaseholds on land (as in the popular 30yr + options route)?