You predict that if it happens again, it will definitely explode. Thats for sure. Because you have a backlog of anger at your boss, and you work in a company, the opportunity to break out is always there. If you want me to give you advice, what should I do with a boss like this? I want to say:
If it really happens again, it will definitely explode. Maybe the boss will pronounce it correctly from now on, then your outbreak is valuable. Because sometimes change comes from strong stimulation.
The main thing is to calm your anger. You need to reflect, is your anger just because of such a boss? Are there any other reasons why you dont understand others well, or your ability to get along with your boss is not enough? Think about it. The initial reason why you are angry is that the bosss pronunciation is not accurate, he uses his native dialect. This is your unfair judgment to the boss. Since he is speaking his native dialect, his pronunciation is his pure local accent, and you define his pronunciation as inaccurate (although there is some truth in this) with the standard of Putonghua, you have already defined his deficiency in your heart. When you communicate with him, you will unconsciously convey the meaning of negation or correction, or show impatience, and the other party will naturally feel that you do not respect him. Even if he is angry, he is worried that you dont understand what he means, not that he denies you or embarrasses you.
I would like to point out that the source of your dissatisfaction with your boss is voice difference, not unreasonable or overbearing. In your anger against your boss, there is also resentment that you unconsciously demand that his pronunciation should conform to your ears. If you can understand in this way, I believe you will alleviate the trouble caused by the lack of others. Then, as long as in that situation, you can calmly and persistently repeat the concept to him: Dear boss, would you please speak Mandarin??
It is best for you to have a sincere exchange of views with your boss: ask your boss to speak Mandarin as much as possible in future calls, or slow down your conversation to avoid misunderstanding. In this way, your boss will certainly appreciate your attitude towards others and your interpersonal skills.