Police stepped up border patrols to prevent petrol being smuggled into Cambodia, where prices have gone through the roof.

Smugglers are using vehicles with enlarged tanks to get the fuel across the border.

Police now record tank levels in vehicles departing Thailand via Aranyaprathet in Sa Kaew and other crossings. When they return they check to see if "unusual" amounts have been consumed.

Some enlarged tanks on lorries can hold as much as 400 litres.

As many as 180 to 200 trucks cross each day.

Police suspect most are smuggling petrol to a storage facility about five kilometres from the Aranyaprathet checkpoint.