OMNI Hotels Asia-Pacific has appointed Lintas Hongkong as the group's advertising agency for its international account, following a credentials and creative pitch by the major Hongkong agencies. Mr Michael Kalyk, the hotel group's president, said: ''We were impressed by Lintas' strategic and analytical ability in approaching our product and their shared vision with Omni. Their efforts reflected in their presentation were most outstanding. ''Our advertising objective is to enhance brand awareness, and we see Lintas as having the ability to assist us in achieving just that.'' Omni currently manages three hotels in Hongkong, one in Singapore and has secured the management contract for a new hotel opening in early 1994 in Ho Chi Minh City. Its ambitious plans foresee expansion of the portfolio from five to 20 hotels in the region in the next several years. Areas targeted include Thailand, Indonesia, Malaysia, the Philippines, Korea, Taiwan, Japan and China. GAVIN Anderson and Co, the corporate and financial public relations firm, has opened an office in Frankfurt, its third in Europe after London and Paris. Mr Michael Radtke, formerly head of international liaison at the Federation of German Stock Exchanges, was appointed managing director of the new subsidiary, which will be known as Gavin Anderson and Co GmbH. Mr Radtke's prior experience was representing the German exchanges in their dealings with companies, exchanges and securities regulators in other countries, advising on listing and regulatory issues abroad. He also served as legal adviser to the speaker of the Board of Management of the Frankfurt Stock Exchange.