The visit to Thailand of a 40-strong Burmese delegation led by Senior General Than Shwe is another step in the junta's campaign to gain credibility in the wider world. If the visitors heard some tough talking from their Thai hosts, they were also accorded a meeting with King Bhumibol in the capital. That seemed in keeping with the stick-and-carrot approach to the constructive engagement policy which the Thais have adopted towards their neighbour. This approach has produced nothing of value for members of the Association of Southeast Asian Nations except to have damaged previously excellent ties with the European Union while producing none of the hoped-for improvements in human rights. But Thailand has a more pressing need to engage with the junta. Burma has overtaken Afghanistan as the world's top opium producer, and is known to be producing ever larger quantities of amphetamines. Thailand's own efforts to cut drug production have been sabotaged as more and more of its young people fall prey to the traffickers. There are reports that half the children in northern Thai schools are known to have tried amphetamines. Apart from its own efforts to curb domestic production, the government in Bangkok has to tackle the problem of drugs from its neighbours. At least half the narcotics smuggled out of the Golden Triangle passes through the country increasing in value along the route - yet few traffickers are ever brought to justice. Things may change now if the two countries really increase their joint efforts, and the Burmese junta promotes its own anti-drugs campaign. So far, it seems to have convinced Interpol of its sincerity, though US drug enforcement agencies and others remain deeply cynical. Co-operation with Thailand in the fight is the surest test of Rangoon's commitment. If that stands up to scrutiny, it will be the first sign that constructive engagement can produce results.