Thailand's finance ministry plans to study a tax on online gold trading and will look at measures to limit gold trading volumes, a senior official said, amid a surge in the baht currency.

The baht has gained 10% against the dollar so far this year to become Asia's best performing currency. It has now reached its highest level against the dollar in more than four years.

Senior ministry official Lavaron Sangsnit said the revenue department would study the imposition of a specific business tax on gold trading conducted via online platforms.

It would also look at measures to limit the volume of gold trading, he told a media briefing.

The Thai baht's gains against the U.S. dollar are being driven by "huge" gold trading volumes, with its rise not in line with fundamentals, Central Bank Governor Vitai Ratanakorn told the same briefing.

The central bank will manage online gold trading, he said, adding that authorities would manage unusually large gold transactions conducted in baht.

Vitai said maximum trading volumes would be established for major gold traders.

The central bank said earlier that it had moved to contain the rapid gains in the baht, ordering tighter scrutiny of foreign exchange transactions linked to gold trading and instructing commercial banks to closely monitor foreign currency inflows.

Earlier, Finance Minister Ekniti Nitithanprapas said the baht was too strong and was hurting Thailand's economy.

-Orathai Sriring, Thanadech Staporncharnchai and Kitiphong Thaicharoen/Reuters