VIENTIANE, June 19 (Reuters) - Thai Hua Rubber PCL, Thailand's top rubber producer, will seal deals next week for the sale 50,000 tonnes of rubber to China at $1.68 and $1.70 a kg, Chief Executive Luckhai Kittipol said on Friday. China is Thai Hua's biggest customer, absorbing 40 percent of the company's annual 300,000 tonnes of rubber exports. (Reporting by Lewa Pardomuan; Editing by Ben Tan)