The gypsum market in Thailand will likely expand at a slower pace this year than in 2004, according to Siam Gypsum Industry (Saraburi) Co, a Franco-Thai joint venture between Lafarge Boral Gypsum in Asia and the Siam Cement Group, the Bangkok Post reports.   Due to the sluggish property market, total sales of gypsum in Thailand are projected to increase by only 10-15 per cent this year compared with growth of 22-23 per cent last year.