VIETNAMESE boat people are threatening to commit mass suicide tomorrow in protest against mandatory repatriation, according to a spiritual meditation group. The Ching Hai Meditation Association said it had received calls for help from the boat people in detention centres seeking new lives overseas. Around 700 to 800 members of the association, who came to Hong Kong from around the world, held banners and wore messages on their clothing during a protest outside the Central Government Offices yesterday. Supreme Master Ching Hai, the British-Vietnamese founder of the organisation, wept as she led the group in songs calling for peace in the camps. Up to 70 written pleas from inmates threatening suicide on the anniversary of the fall of Saigon had been received, she said, and urged the Government to reconsider its repatriation plans. ''These people have told us through the letters that they would rather die than return to Vietnam. We and the Hong Kong Government cannot allow that to happen.'' She said ''force and brutality'' was used by security and police within the camps and inmates should be treated more humanely. The raid on the Whitehead Detention Centre three weeks ago was a classic example of security forces' tactics, she said. ''These people are our fellow human beings and should be treated as such. Many of these people threatening to kill themselves have families who they need to look after. The Government musn't allow them to die,'' she said. The Government Refugee Co-ordinator, Brian Bresnihan, said detention was the cornerstone of Hong Kong's policy on boat people and any found to have non-refugee status must be returned to Vietnam. ''Rumours abound in detention centres and we take them very carefully. We will monitor the situation on Saturday closely,'' he said. Representatives from the United Nations High Commissioner for Refugees, the Community Services Department would be at the camps, and staff from other organisations would offer support and counselling to inmates, he said. The meditation group plans to return to the government offices tomorrow for a smaller protest with the majority of members heading to Whitehead and High Island detention centres in the morning and afternoon respectively, to continue their peaceful protest.