I want to request my manager to provide a round trip ticket
When I went my last vacation I paid for the air ticket. Now I am entitled for company ticket. Please provide a round trip ticket for my next vacation.
When I went on my last vacation, I paid for the air ticket myself. Now I believe I am entitled to a company ticket. Please provide a round trip ticket for my next vacation.
This is more of an order than a request. It might be useful for you to explain why you think you are entitled to a company ticket, perhaps cite the company handbook or your job contract. If you are certain that they should provide the ticket, your letter should include the details of when and where you would like to go as well as the personal information needed to procure the ticket so that the company can fill your request. If you are uncertain, it might be better to say "Can you please confirm that the company will provide a round trip ticket for my next vacation?" That way you won't come across as demanding, and if you are wrong there will be less chance of hard feelings.