invitation letter

To visit Singapore ("SG") on a vacation you may or may not required a sponsor or someone should live here to provide an invitation letter in order for you to get a visa.

e.g. If you don't know anyone (local contact) in SG and your purpose of visit is for site seeing (tourism), then you may obtain LOI ( Letter of Introduction) from your country embassy. Normally, this is done by authorized travel agency (mentioned in below link), and other details can be found from this link as well.

https://www.ica.gov.sg/page.aspx?pageid=168

Subsequently you should check with your local agent who is arranging VISA for you. He should help you in this regard.

Since sponsoring someone for a visa involves great financial responsibility (e.g. for his/her incarceration and deportation in case he/she does something wrong), it is unwise to sponsor somebody you don't know very well (close friend or family member).
It is also not allowed to solicit invitation letters on this forum or approach forum members for visa sponsorship. So please don't!
The professional (and paid) ways to get a visa that Surya pointed out above are your only options.

thanks a lot brother

you were too useful
I will apply for Letter of Introduction (LOI) this week

Dear
did you got Letter of Introduction (LOI) or visa?

Not yet

We want more informations about that,
Is there any association or people to help ?

Nacih, let us know what exactly you want to know as we have provided enough information that on a visit to Singapore the best way to get the visa is contact your local travel operator who must be doing or helping to obtain visa for their travellers visiting Singapore. Or else visit Singapore embassy in your respective country to get further details.

NACIH wrote:

We want more informations about that,
Is there any association or people to help ?

About what exactly would you like more information - and an association for what?
As Surya said above, a travel agent can help you to get a tourist visa for Singapore.