The junta announced earlier that the visa waiver would be in effect from Aug 1 to Oct 31 to celebrate 39 years of strong Thai-Chinese relations and boost tourism.
"We want the junta to provide clear information about when the waiver will be in effect, otherwise we may have to pay the visa fee and tourists will be confused," said Sisdivachr Cheewarattanaporn, president of the Association of Thai Travel Agents (ATTA).
ATTA said the waiver will benefit tourism in the second half of the year. It expects it will help attract 800,000 to 900,000 Chinese visitors during the period.
ATTA reported the number of Chinese tourist arrivals through its members sharply dropped by 57.3% to 374,821 in the first half.
Chinese tourists are forecast to reach 3.98 million this year, providing revenue of 158 billion baht, down from 4.7 million visitors and and 182 billion in revenue in 2013.