HONGKONG pop stars Sally Yeh and George Lam Chi-cheong will be playing a series of joint concerts in Beijing next month, supporting the city's bid for the 2000 Olympics. The concerts will be held at the Capital Gymnasium on August 6-10, shortly after Yeh's July concert series ends in Hongkong. ''It will be quite tiring, since I will be holding concerts in July,'' Yeh said yesterday. However, the Taiwan-born singer who was raised in Canada is excited about working with Lam in the fund-raising concert to promote Beijing's bid. ''I'm very happy about this, and it will be quite fun to work with George,'' she said. Lam echoed the sentiment and said he hoped some of China's most famous athletes would make guest appearances. The duo's five-night event will not only be their first major concert series together, but it will also break the record for the most shows any Hongkong artist has held in Beijing. They will move on to Changsha, in Hubei province, for two days following the concerts, to promote the Olympic bid there. Both singers are well known in China - even in the remotest parts of the country. As far as the Xinjiang Autonomous Region, their voices can be heard from loudspeakers blaring from inside music shops. Yeh and Lam last appeared together at Yeh's AIDS awareness concert in November. Tickets for the Beijing shows will be sold for the equivalent of about $80 to $200 in China. A limited number of tickets will be available in Hongkong. Proceeds will go to the Beijing Olympic bid committee.