Thailand's Advanced Info Service Pcl said on Tuesday Huawei Technologies is among five companies tendering to build its 5G core networks.
AIS' disclosure came as the UK government ordered Huawei equipment to be purged completely from the country's 5G network by 2027 amid U.S. calls on its allies to exclude the Chinese company from their networks on security grounds.
Thailand, the United States' oldest ally in Asia, has said it would not exclude Chinese vendors from building its 5G infrastructure but would stay mindful of any security issues.
AIS, Thailand's largest mobile operator, is near the final stage of selecting vendors, which now include the world's biggest telecoms equipment maker Huawei, Ericsson, Nokia, ZTE and Samsung, said the company's president Hui Weng Cheong.
"We are in the process of selecting vendors for the proper 5G core networks, both the Chinese and the Europeans," said Hui, naming the five companies in a briefing.
"When we do anything, we send our request for proposals to all five, because we don't want to pre-select," he said.
Hui's comment came after AIS announced last week a partnership with Huawei to sell 5G smartphones by the Chinese company.
Huawei has repeatedly denied U.S.-led allegations that its equipment could be used by Beijing for spying.
Hui said AIS, which won 23 5G spectrum licenses in February auctions, is aware of the U.S. allegations around the Chinese company but it will protect itself.
"Those claims are not proven ... but when we use the Chinese vendors, we'll also have very important clauses specifying what they shouldn't do, to protect ourselves," he said.
Last year, Huawei set up a 5G testbed in Thailand, its first in Southeast Asia.
Last month, Singapore's biggest telecoms operators said they had selected Nokia and Ericsson over Huawei to build the 5G core networks.
Singapore Telecommunications, which has stakes in AIS, said it had selected Ericsson to negotiate the provision of core and other networks.