The U.K. firm has entered into an exclusive alliance with Yangon's three-lawyer U Tin Yu & Associates.
The ASX-listed plaintiff's firm has already inked deals to acquire three British law practices for $36 million.
The British firm says the new office will focus on advising Chinese energy and mining companies on outbound transactions.
The 400-lawyer U.K. firm will have two partners stationed part-time in its new office.
Singapore's largest firm has entered into a non-exclusive deal with Jakarta's Assegaf Hamzah & Partners.
The new office, which will open July 1, will be the Japanese firm's third domestic branch.
The office will initially be led by legal director James Zhang, a former partner at Beijing's Zhong Yin Law Firm.
The international firm has linked up with Jakarta's Ivan Almaida Baely & Firmansyah Law Firm.
The Japanese law firm said it will open Yangon and Bangkok offices in May and July, respectively.
A significant amount of yen is flowing into Southeast Asia as Japanese companies seek growth outside the country. The lawyers aren't far behind.