Myanmar will charge up to 61 illegal Thai nationals working on secret rubber plantations near the Thai-Myanmar border.

In a detailed report, Myanmar's state-run New Light of Myanmar newspaper said the Thai nationals -- 52 men and nine women -- were arrested earlier this month in what appears to be a major crackdown on illegal rubber growing operations in the Taninthayi region.

The military moved in on the plantations and made the arrests without firing any shots, the report said.

Separate raids by the army on a 1,000-acre operation and a 500-acre plantation netted an array of rifles including M-16s, AK-47s, Winchesters and revolvers as well as ammunition.

The army also confiscated three bulldozers, 17 vehicles, five backhoes and 20 motorcycles.

The isolated plantations were also connected to the Thai border by rough dirt roads.

Taninthayi is an administrative district covering the long narrow southern part of the country on the Kra Isthmus, the extreme south of Myanmar that borders the Andaman Sea to the west and Thailand to the east.

Kawthoung Township is near the most southern tip of the region.

Much fishing is carried on along the west coast of Taninthayi.

However, the eastern area is isolated and mountainous with only a few roads, mostly dirt and gravel and often serving forestry and rubber plantations.

The arrests and possible charges come as Myanmar's President Thein Sein announced he will visit Thailand July 22 for three days, a trip he has twice postponed, the last time at the beginning of June.

He was believed to be dissatisfied with the massive publicity surrounding Myanmar's opposition leader and pro-democracy advocate Aung San Suu Kyi during her own trip to Thailand at the time, a report by Mizzima news Web site said.

Thein's trip to Thailand is part of the government's move toward a more open democratic society and a more openly business-friendly one that encourages foreign investment for natural resource exploitation.

While the New Light report points to charges for the illegal Thai workers, it remains to be seen if the government will follow through or quietly release the workers.

New Light also said the Thai workers "are safe and Myanmar officials have informed Thai officials about their detention."

The report also said Myanmar, too, has had to deal with its own nationals working illegally in neighboring countries, although New Light didn't mention Thailand by name.

Rubber along with jute and cotton now are big-business crops for Myanmar, which competes with other Asian countries on the open market. But Rubber also is open to hugely fluctuating prices.

In November the Myanmar Rubber Planters and Producers Association said it was hoping to export 100,000 tons of rubber in the fiscal year 2011-12.

In 2010-11, Myanmar exported around $303 million worth of rubber, the association said.