Add PlumiBot to the group, then type !lang add vi, !lang add id, and so on — one line per language you need. From then on every message posted in the group is translated into all of them at once, in a single reply. There is no pairing step and no limit in any plan on how many languages a chat can carry.
Almost every translation tool on LINE — including LINE's own interpreter accounts — is built around a language pair. That works for two people. It stops working the moment a third language enters the room, which in practice is most working groups: a site foreman writing Chinese, workers reading Vietnamese and Indonesian, a client who only reads English.
The instinct is to add a second bot for the second pair. That is the one approach that reliably fails, for reasons worth understanding before you try it — two translation bots in one groupcovers what actually happens.
Add PlumiBot as a LINE friend, then invite it into the group the same way you would invite a person. A new group starts with English and Traditional Chinese switched on. From there:
PlumiBot
!languages to see what the chat is currently translating into. Each language comes with a button, so most people never type a command again after this.!lang add vi for Vietnamese, !lang add id for Indonesian, !lang add th for Thai. There are 126 to choose from.!lang remove en if nobody in the group reads English.After that, nobody has to do anything. Somebody writes 明天七點開工 and the same message comes back as Vietnamese, Indonesian and English, in one tidy block per language. No one picks a target, no one taps translate, and nobody has to know which language anyone else reads.
The group's language list decides what messages are translated into. It does not decide what language the bot speaks to you in — its menus, errors and confirmations. That is per person: type !setlang vi and PlumiBot talks to you in Vietnamese while everyone else keeps their own setting.
Less than you would expect, because languages are not billed as separate translations. All of them are produced in one pass: the message and the conversation around it are read once, and only the written-out translations add up. A second language therefore costs far less than a second translation would — and a fourth costs less again, relative to what you get.
The Free plan is 105,000 tokens a month, which is roughly 300 messages for a typical two-language group. Adding languages brings that number down, but much more slowly than the number of languages goes up. If a group outgrows it, the paid plans buy tokens rather than features — nothing is locked behind them except voice, photos and link reading. See pricing.
If your group only ever needs one pair — two friends, one Japanese, one English — none of this buys you anything, and LINE's own free interpreter account for that pair may be all you need. Multi-language translation earns its keep when the number of languages in the room is genuinely greater than two and changes over time.
And if what you actually want is a LINE OpenChat, note that OpenChat has translation built into LINE itself, at no cost. Ordinary group chats — the kind most workplaces and families use — do not.