Thailand's celebrity Chinese panda Lin Hui must be wondering why patrons who came to wish her a happy birthday were all wearing masks and standing at least one meter apart.

Chiang Mai zoo in Thailand's north on Monday celebrated the 19th birthday of giant panda Lin Hui, offering her an ice cake filled with fruit as a birthday gift.

The Chinese consul general in Chiang Mai, Chiang Mai zoo director and panda fans participated in the celebration at Lin Hui's air-conditioned enclosure, all donned in face masks and singing birthday song to Lin Hui while observing social distancing.

A nine-tiered ice cake, filled with fruit, were placed before the over-joyed panda, now weighing 125 kilograms.

Lin Hui arrived in Chiang Mai on loan from China at the age of two in 2003.

Lin Hui's care-takers said that the panda can understand simple Thai words, especially when called upon with bamboo leaves.

Meanwhile, a flower-laying memorial ceremony was held for the passing of Lin Hui's late partner Chuang Chuang who passed away last year from heart failure.

Chuang Chuang had also been a loan from China to Thailand since 2003.

Both Chuang Chuang and Lin Hui successfully artificially bred and produced an offspring named Lin Ping in 2009.

Lin Ping also became a celebrity in Thailand since then, drawing tourists from all corners of Thailand to Chiang Mai Zoo to see the new born cub.