THE vacancy rate in Bangkok's commercial property market will peak at 25-27 per cent next year, but strong economic indicators will bolster market confidence and push vacancy levels down in 1995, according to a research by Colliers Jardine's Thailand office. ''Continuing strong economic growth and the likely postponement of some projects planned for 1995 should prompt a reduction in vacancy levels,'' said Mr Roger Cook, chief executive officer of Colliers Jardine. About 15 million square feet of office space is now under construction, of which only 3.2 million sq ft is already committed. Current stock levels of office space are around 30 million sq ft, with a vacancy factor of around three to five per cent, according to Colliers Jardine. Vacancies are mainly due to an increase in supply as office space now under construction comes on to the market. But Colliers Jardine note that vacancy levels will vary. ''Well-located, well-specified properties will continue to lease,'' said Mr Cook. Colliers Jardine forecast an annual average take up of around 3.2 million sq ft over the next two years, which is an increase on previous levels. During this year and the next, Mr Cook expects tenants to capitalise on opportunities available as a result of the short-term oversupply. Colliers Jardine's report divided supply into different areas of Bangkok. Findings showed that vacancy levels are likely to be highest in the southwestern sector of the city. In this sector, 43 per cent of the available space is being constructed. The study concludes that the overall outlook for the commercial property market is positive. ''Market confidence fuelled by continued strong economic performance will ensure that owners with quality developments will be rewarded with strong rental and high occupancy levels,'' said Mr Cook.