Whats the rule that makes "please" pronounced the same as "p...

There's no rule.

Pleas is spelled <pleas> because it's the plural of pleas.

If you're curious about why a word is spelled the way it's spelled, your first recourse should be etymonline dot com.

Here's Why This Year Will Be "Different" For Taylor Swift And Travis Kelce - BuzzFeed

While you may reasonably ask why words are spelled the way they're spelled, it makes no sense to ask why they're pronounced the way they're pronounced.

Please is an anglicization of the French word plaisir.

You'll usually find your answer there.

Imagine we could fly into space and take a selfie of our galaxy. This spacecraft made the most detailed map of the Milky Way ever - BBC Sky at Night Magazine

Whence the <ea> I cannot say but some other words that were spelled <ai> in French are spelled <ea> in English: aise → ease, graisse → grease, fait → feat.

Back in the day (circa 1300), it was written <plesen>.

Words are pronounced the way that they're pronounced.

Trump administration’s deep cuts to public health leave system reeling - PBS

What's (not “whats”) the rule?

Whats the rule that makes "please" pronounced the same as "pleas"?

Read also: