Hi,purchased a Proton Persona 2011 factory fitted cng at auction 5 years ago and its been trouble free cheap motoring so far.Because its dual fuel I get a yearly inspection done on the gas installation when I pay road tax each year at a cost of 500 bht. ,This year it will be 10 years old I know lpg tanks have to be replaced evey 10 years as I also have a LPG car Anybody know whats the script with CNG/NVG tanks they are similar to a diving cylinder that has to be hydraulicly tested every few years .I have looked on google and cant find any info on the regulations in thailand in english.