I am a tourist working remotely for my own company while in the US.

Technically you need a visa. Practically as long as invoices are coming from your own country and the money is going to your own country, nobody will care (or even notice).

Unless of course you make posts like this one in a public forum under a name everyone knows you under. But I am counting on inefficiencies and the good will of fellow hackernewsers. (you'd need to actively get reported for anything to happen)

PS: having an actual tourist/business visitor's visa rather than just the visa waiver (esta) makes things easier and border crossings go much smoother