Mix the cucumbers and sea salt together in a bowl, let stand for 30 minutes to let the cucumbers soften. Drain, and rinse with fresh water.
While the cucumbers are standing in salt, whisk together the sugar, vinegar and water in a saucepan; bring to the boil. Reduce heat, and stir in the chilli bean sauce and hot chilli oil.
Mix the cucumbers with sliced chillies, onion and garlic in a heatproof airtight container, and pour the hot vinegar mixture over the vegetables. Cover and refrigerate for 2 to 3 hours to blend the flavours. Serve chilled.