Plausible? Yup. The way you're thinking about it?... Not so much.
Of course it's plausible. SciFi has had pleasure planets since the dawn of writing. That's not the problem.
Some of your conditions don't make sense. Unless you have a galactic empire with near instantaneous travel and very instantaneous communication, you won't have "corporations" the way you're thinking. That's very today-Earth where enough governments are larger than global corporations that they're still playing second-fiddle.
Your corporation owns and operates an entire planet. That's indistinguishable from a government. Your planet will have every conceivable job, from child care and janitorial through education and professional white-collar to government and administration. You'll have homes and factories and offices and grocery stores, and movie theaters.... People will be born, live and die having never left your planet. The fact that the letters "Inc." appear after the government's name has no practical meaning.
And that means your government will be subject to espionage, sanctions, and war just like any other government. Where there be no rules, there be no rules, and all the other
corporations governments in the galaxy will treat you as they are treated — according (or not) to corporate agreements and contracts treaties.
As for following laws — you had better believe corporations follow laws, even if they're their own! A planet full of amusement park rides? The logistics in materials, food, people... it's staggering! You'll have policies, procedures, regulations, directives, statutes, mandates, ordinances... and laws... running out your ears. Your corporation's legal department might be second only to the finance department. Heck, I've worked for corporations where their employee policy "manual" had volume numbers. Yours will require a library.
In other words, you seem to have a low appreciation for the need for administration. Your bureaucracy will number in the millions. You'll have police and spies and a military and tax collectors and firemen and hospitals and schools and libraries and places-where-people-can-complain and every other trapping of traditional government. The only labor force larger than your bureaucracy will be ride operators. And the only distinguishing factor between your corporation and a government is that you might (maybe) be able to stop those ride operators from forming a union.
Look at our planet and what it takes to manage its day-to-day affairs. Your planet won't be any different. Other than the organization in charge will have something like "Inc." at the end of its name.
A rose by any other name still stinks like a kettle of rotting fish.