The Civil Aviation Authority of Thailand said on Wednesday it is suspending the use of the Boeing Co's 737 MAX 9 due to safety concerns.
The regulator said it will temporarily suspend the use of Thai Lion Air's Boeing 737 MAX 9s for seven days, starting on Thursday and will continue to investigate safety measures. Thai Lion Air's three MAX 9 jets will be affected.
Its parent company, Lion Air, has confirmed reports it has put on hold the scheduled delivery of four Boeing 737 Max 8 jets while it waits for the outcome of the Indonesian investigation into its October crash that killed 189 people.
Speaking at a transport ministry news conference in Jakarta about the grounding of Max 8 planes, Lion Air executive Daniel Putut said the airline needs to know the "root cause" of the accident.
Lion Air ordered 222 Boeing Max planes, including 218 of the Max 8 model and four Max 9 planes. It currently has 10 Max 8 planes in its fleet.
Thailand is the last country in Asia where the jets are registered to issue a suspension, following the fatal crash of a MAX 8 jet in Ethiopia on Sunday.
Thai airlines do not operate MAX 8 jets.
Earlier on Wednesday, Hong Kong barred Boeing 737 MAX airliners from its airspace.
Despite Boeing's assurances in the wake of the disaster, the European Union, Britain and India joined China and other countries grounding the plane or banning it from their airspace as they await the results of the crash investigation.
The semi-autonomous Chinese city's Civil Aviation Department (CAD) said it was imposing a temporary suspension from 6 pm local time (5pm in Thailand) on Wednesday until further notice on "operation of Boeing B737 MAX aircraft into, out of and over Hong Kong".
The ban is "solely a precautionary measure to ensure aviation safety and protect the public", a CAD spokesman added.
The department added it had been in close contact in the past few days with the US Federal Aviation Administration and relevant organisations, including two airlines -- India's SpiceJet and Globus Airlines of Russia -- that have recently used the 737 MAX for flights to Hong Kong.
SpiceJet had defended the jet on Tuesday, describing it as a "highly sophisticated aircraft".
Hong Kong flag carrier Cathay Pacific does not have any 737 MAX aircraft in its fleet.
On Sunday, a new Ethiopian Airlines 737 MAX 8 went down minutes into a flight to Nairobi, killing all 157 people on board.
The crash came after a Lion Air jet of the same model went down in Indonesia in October, claiming 189 lives.
Several airlines have grounded the MAX 8s in their fleets, but many others are continuing to fly the plane pending an investigation into the crash and possible guidance from Boeing itself.