BANGKOK -- Private hospitals in Thailand are trying to attract more foreign patients to make up for lost revenue after the government capped how much they can charge Thais.

Bangkok-based Phyathai Hospital, an affiliate of locally listed Bangkok Dusit Medical Services, Thailand's biggest hospital, opened a new facility earlier this year to provide high-level care to foreign patients. The company invested 10 billion baht ($325 million) to renovate buildings, add new equipment and set up specialized laboratories.

The new complex has centers specializing in aortic care, neurology, and trauma and replantation -- reattaching severed body parts. Anantasak Apairatana, the hospital's executive director, said the hospital aimed to raise the share of foreign patients from 25% at present to 40% by the end of the year.

Since the government began promoting medical tourism some years ago, private hospitals in Thailand have competed to attract foreign patients. One advantage they offer is affordable prices. A heart bypass operation that might cost $123,000 in the U.S. or $17,000 in Singapore goes for around $15,000 in Thailand.

According to the Tourism Authority of Thailand, there were 3.42 million visits to Thai private hospitals in 2018 by foreign patients, including both tourists and foreign nationals living in Thailand. They generated total revenue of 140 billion baht.

In all, private hospitals in Thailand bring in around 500 billion baht a year. The industry already depends on foreigners for nearly 30% of its revenue. The need to pull in more cash from foreign patients to offset falls in income from Thais has accelerated the trend. In May, the government imposed regulations limiting the profit margins of private hospitals.

The law requires all such hospitals to disclose to authorities charges for widely used medications, supplies and services. They are also required to disclose prices to patients. This price transparency is promoting competition.

Prices for about 3,900 medications have been put on a government "price control list," which sets limits on profit margins for those products, mostly to less than 10%. All price increases for medications on the list must be approved by a government panel.

Responding to public complaints about overcharging, the previous military government ordered a special committee to monitor pricing at private hospitals in Bangkok. The committee found that drug prices at some hospitals were 10 times their cost.

"This measure was put in place to allow patients to see how much they have to pay before they begin treatment. It will give them the ability to choose which private hospital they can afford," said Wichai Pochanakit, director-general of the Ministry of Commerce's Department of Internal Trade, which oversees the price control list.

The new rules have clearly had an impact, although CEOs of major hospitals declined to say how their bottom lines have been affected. Among big private hospitals listed on the Stock Exchange of Thailand, Bangkok Dusit and Rama 9 Hospital saw their net profits for the June quarter decline 10% and 29%, respectively, from a year earlier.

Thonburi Healthcare Group, which runs the Thonburi Hospital chain has spent 4.2 billion baht to win more business from overseas patients. Of the total, 4 billion baht was poured into the 600-bed Thonburi Bamrungmuang Medical Center, which opened in February in Bangkok.

The hospital offers in vitro fertilization, cosmetic surgery, treatment for diabetic ulcers and a digital dental center. "At the Bamrungmuang, we expect up to 95% of patients to be foreigners, who are willing to pay the extra cost of specialized medical services," said Boon Vanasin, founder and chairman of the group.

Foreign patients spent an average of more than 35,000 baht per day at Thai hospitals, nearly three times the roughly 18,000 baht per day that Thais spent, according to research by Thonburi Hospital. The new unit generates average revenues of 100 million a month, according to the company.

But seeking additional business from well-heeled foreigners is risky: The new investments and marketing cost money.

"With many private hospitals targeting foreign patients, it makes competition more intense. Some hospitals even have their agents advertise and do promotions abroad to attract patients, particularly in China," said an analyst at Krungsri Research.

What is clear is that the new government policy, aimed at winning public support, has forced private hospitals to rely even more heavily on patients from abroad.

Private hospitals, which have invested hugely in new technology, are likely to charge more for medical care to break even. That is the main reason for their focus on affluent foreign patients, rather than providing health care to the poor, according to a study by the Government Saving Bank.