SINGAPORE Airlines will operate more non-smoking flights from this weekend. On Sunday, all services between Singapore and China and between Singapore and New Zealand, will become non-smoking. SIA operates 16 weekly flights to China and six to New Zealand. In addition, SIA's Singapore-Taipei-Seoul service, which operates five times weekly, will be smoke-free. With SIA's wholly-owned subsidiary, SilkAir, operating smoke-free flights on all its services, 79 per cent of the SIA Group's network will by the weekend be smokeless. THIS week a delegation of 10 Australian travel industry representatives is visiting Guangzhou, Shanghai and Beijing in an effort to boost tourism Down Under from China. ''China will become a large and important market for Australia within the next decade,'' said John Morse, regional director (Asia) for the Australian Tourist Commission. ''There is already considerable Chinese interest in Australia as a business and investment destination, and there is no doubt that tourism development will follow.'' More than 22,000 mainland Chinese visited Australia last year, a rise of more than 20 per cent over 1992. MORE than 100 travel agents from Hong Kong have been in Dubai for the 16th International Chinese Tourist Association Overseas Convention. The ICTA is looking at the United Arab Emirates as a new destination for package tours now that Emirates flies daily between Hong Kong and Dubai. The ICTA delegates also visited Turkey. NEW Zealand's tourism industry achieved record growth last year with international arrivals of 1.15 million, up 10 per cent on 1992.