BANGKOK, Thailand -- Thailand's coup-installed Defense Minister Prawit Wongsuwon will be in Washington from April 22-27 to meet Defense Secretary James "Mad Dog" Mattis, boosting the junta despite demands for elections, human rights, democracy and Mr. Prawit's resignation for alleged corruption.

"The U.S. needs to counter China's increasing rise in interests and influence in Thailand, and in Southeast Asia by extension, and deepening already deep military-to-military relations is one way to do that," Benjamin Zawacki said in an interview, describing retired army general Prawit's visit.

"Thailand's government is -- as all Thai governments have been since the turn of the century -- pro-Beijing. And until Trump came to power, it was anti-Washington as well," said Bangkok-based Mr. Zawacki, author of a new book titled, "Thailand: Shifting Ground Between the U.S. and a Rising China."

Thailand publicly says it wants good relations with all nations, and is not leaning toward China to the detriment of the U.S.

Mr. Prawit's meeting with Mr. Mattis and other Pentagon officials "affirms both sides' commitment to the longstanding [non-NATO] alliance, and our shared interest in advancing prosperity and security in the Asia-Pacific region," a U.S. Embassy spokesperson said.

They will discuss ways "to strengthen our alliance and advance regional security," the embassy said.

Mr. Mattis led a U.S. delegation to Bangkok in October as President Trump's special envoy to attend the royal cremation of King Bhumibol Adulyadej.

After Mr. Trump became president, the State Department and its diplomats muted their initial criticism of Thailand's 2014 coup and current military government, which had caused rifts between the two countries.

In contrast, the Pentagon stepped up its relations with Thailand's politically powerful U.S.-trained army.

"In 2017 alone, $261 million worth of military deals are in the works," U.S. Ambassador to Thailand Glyn Davies said in July.

The Pentagon's support for the military regime "further legitimates this government's hold on power and approach to governance," Mr. Zawacki said.

The U.S. also increasingly depends on Thailand to shrink North Korea's regional financial and diplomatic support.

In 1950, Thailand was the first Asian nation to send troops under the United Nations to support the U.S.-led Korean War.

Among Thailand's more than 6,300 soldiers in Korea, more than 1,100 were reportedly injured and 136 killed.

During the 1960s and early 70s, Thailand's territory was extensively used for U.S. airbases and other facilities when America waged its failed wars against Vietnam, Cambodia and Laos.

More recently, the U.S. sent more than 6,000 troops to its 37th annual multinational Cobra Gold military exercise in Thailand during February.

The lowest point came during World War II when Thailand sided with Japan and declared war on the U.S., resulting in U.S. warplanes bombing Thailand to degrade its support for Japanese forces inside the country.

Mr. Prawit meanwhile is under investigation by the regime's National Anti-Corruption Commission after 22 luxury wristwatches were discovered in his possession, valued at more than $1 million.

Mr. Prawit, who is also an influential deputy prime minister, insists the watches are not evidence of corruption because they were loaned to him by a now-dead wealthy friend.

Thousands of Thais signed several online petitions demanding Mr. Prawit resign over the wristwatch scandal.

"If the people do not want me, I will leave," Mr. Prawit said in February, but he did not quit.

Thai media, anti-junta activists and others suspect the investigation will not result in any punishment because Mr. Prawit enjoys strong support from Prime Minister Prayuth Chan-ocha who seized power in a bloodless 2014 military coup.

Mr. Prayuth met President Trump during an official visit to the White House in October and said at their dinner, "I am happier than at any time in the past, as I feel that I have found my true friend."

When U.S. Joint Chiefs of Staff Gen. Joseph Dunford visited Bangkok in February, the two men discussed elections.

Mr. Prayuth said: "I told him, the U.S. president [Trump] has his 'America First.'  I also have a 'Thailand First' as an approach to take care of the country's interests."

The election's "timing will be determined by me and legal procedures," Mr. Prayuth, a former army chief, said he told Gen. Dunford.

Mr. Prayuth is under fire for repeatedly postponing  nationwide elections which, even if held, would limit politicians to a future 750-member parliament that would include a 250-seat Senate appointed by the junta.

Mr. Prayuth orchestrated a new constitution which allows a hung parliament to appoint an unelected person to be prime minister, prompting widespread suspicions that he wants to extend his rule.

An alternative would be for Mr. Prayuth to join a political party and become their elected candidate in polls scheduled for February.

"I have not made a decision whether to accept any of the parties' invitations yet," Mr. Prayuth said on April 9.

His junta is also cracking down on a small upsurge in anti-junta protests.

After a handful of Bangkok's Chulalongkorn University students raised a banner labeling him "the dictator" during his recent on-campus appearance, the military went to their homes and questioned their parents about their children.

The regime did not intimidate the parents, according to government spokesman Lt. Gen. Sansern Kaewkamnerd.

"It was a normal job. They did not carry weapons or drive a tank to their homes," Lt. Gen. Sansern said.