The Energy Ministry plans to deal with the long-running nuisance of smuggled crude palm oil from neighbouring countries by colourising purified biodiesel at palm oil crushing facilities.
The stock of crude palm oil in Thailand exceeds the tally of that produced by farmers, so smuggling is suspected.
Energy Minister Sontirat Sontijirawong said the ministry is overseeing the plan to colourise the purified biodiesel or B100 before blending with diesel oil for B7, B10 and B20.
The traditional colours for petrol and diesel are red, green, purple and blue.
"If the B100 resources have different colours, authorities can spot crude palm oil that has been smuggled in," he said.
"The ministry is processing this plan in line with the shift to B10 from B7 starting in January 2020. B7 will be downgraded from a fundamental diesel to an alternative."
Mr Sontirat said the Energy Business Department will colourise B100.
Before B10 becomes the main diesel option in early 2020, Thai producers have to comply with an global B100 standards for monoglyceride and moisture content.
B10 will absorb 2.2 million tonnes of surplus crude palm oil a year, two-thirds of the total supply, he said.
"A third of the supply is used for palm oil in the food sector."
Mr Sontirat said B10 will be the permanent diesel option because it can tackle the smog crisis in urban areas.
"Crude palm oil is the main raw material for oleochemical production in the future, so this industry should be better managed on the supply side," he said. "Prices of finished oleochemical products are 10-20 times higher than those of crude palm oil."