2.1 Should/could
           We use modal or auxiliary verbs ‘should’ and ‘could’, adverb ‘pleases’ when giving polite suggestions and requests to foreigners about do’s and don’ts in Thailand.
           โครงสร้างไวยากรณ์ในบทนี้จะเน้นการใช้กริยาและคำคุณศัพท์ ในการให้คำแนะนำและการขอร้องอย่างสุภาพเกี่ยวกับสิ่งที่ควรทำและไม่ควรทำในแหล่งท่องเที่ยวในเขตโคราชจีโอพาร์คสำหรับชาวต่างชาติในประเทศไทย

2.1.1 We form subject+should/could+infinitive for a positive sentence. Examples are as follows.
           You should be quiet inside the ordination hall because it is respectful to be so inside a religious place.
           You could pay respect to the sandstone Buddha image.

2.1.2 We form a negative sentence of should/could with should/could +not+infinitive. Examples are as follows.
           You should not pick up any fossils because it is illegal in Thailand and it can destroy the fossils.
           You could not climb the escarpment because it is not safe.

2.2 Please

2.2.1 Please is used as an adverb to mark politeness in requests and in giving polite suggestions in this unit. We form the sentence by using please+infinitive. Examples are as follows.
           Please take all your belongings with you because it is for your own safety.
           Please beware of pickpockets because it is not safe in crowded places

2.2.2 We form a negative sentence of please with please+do not+infinitive. Examples are as follows.
           Please do not leave your belongings on the bus because it is not safe.