Finance Minister Apisak Tantivorawong has pledged to go ahead with the windfall tax plan despite opposition from land developers.
Apisak said he will push forward with the plan to expand the tax base.
He said the tax rate would be about 5 per cent over the appreciation of the value of land and buildings which benefit from the infrastructure projects like mass transit.
Currently the ministry is holding public hearings on the bill, Krungthepturakij newspaper quoted him as saying.
"Although property developers expressed their opposition [citing the windfall tax will duplicate the land and building tax and lead to rising costs], we will go ahead. I am not surprised they oppose it," he said.
Thailand's major sources of tax revenue come from consumption tax and income tax. Taxing the wealthy accounts for only 1 per cent of the total tax revenue, he said earlier.
The country suffered from a wide income disparity and the windfall tax might narrow it.
The government is under pressure to provide welfare for those who live under the poverty line and other lower income groups, with 14 million people recently registering to receive financial support from the government.