ผู้ที่

The expression ผู้ที่ (phûu thîi) is a compound of ผู้ (phûu - agent/person) and the relative pronoun ที่ (thîi - who/that).

1. For Humans and Higher Beings:
ผู้ที่ (phûu thîi) is used for human beings, divine beings, and spirits (e.g., ผู้ที่อยู่บนสวรรค์ phûu thîi yùu bon sà-wǎn - those who are in heaven, ผู้ที่ล่วงลับไปแล้ว phûu thîi lûang láp pai lɛ́ɛo - those who have passed away). For ordinary descriptions of animals or objects, use their noun followed by a relative marker. Personification and entities treated as people are special cases.

2. Formal Register and Public Announcements:
This pattern is the standard choice for formal writing, legal documents, and public announcements. It is the standard way to say "Those who..." in general statements. In everyday conversation, speakers use คนที่ (khon thîi) instead. Using ผู้ที่ (phûu thîi) with friends can sound more formal; that is a choice of register, not a grammatical error. Note that for conditional legal warnings or statements meaning "Anyone who..." or "Whoever...", the term ผู้ใด (phûu dai) is often used instead (e.g., ผู้ใดฝ่าฝืน... phûu dai fàa-fʉ̌ʉn... - Whoever violates...).

3. Describing Groups by Traits:
Because Thai adjectives function as stative verbs, you can use ผู้ที่ (phûu thîi) directly with adjectives to describe groups of people by their traits or conditions (e.g., ผู้ที่บาดเจ็บ phûu thîi bàat jèp - those who are injured).

4. Singular and Plural Usage:
ผู้ที่ (phûu thîi) is invariant and can refer to one person or many people. To emphasize plurality in formal contexts, it can be preceded by words like 'เหล่า' (lào) or 'บรรดา' (ban-daa) (e.g., เหล่าผู้ที่... lào phûu thîi...).

5. Grammatical Function:
ผู้ที่ (phûu thîi) is a noun phrase (the head noun 'ผู้' phûu plus the relative pronoun 'ที่' thîi) that acts as the subject or object of the main clause. The word 'ที่' (thîi) alone introduces the relative clause.

6. Formal Shorthand:
In official headers, legal rights, or lists, the 'ที่' (thîi) is often dropped to create a concise title. For example, 'ผู้มีสิทธิ' (phûu mii sìt - The person who has the right) instead of 'ผู้ที่มีสิทธิ' (phûu thîi mii sìt). This ผู้ + Verb structure describes a status or condition.

7. Higher-Register Variant: ผู้ซึ่ง:
You may also encounter ผู้ซึ่ง (phûu sʉ̂ng) (using ซึ่ง). This is another formal way to introduce a clause describing a person. Do not assign these Thai words a fixed division based on English defining versus non-defining clauses.

8. Standing Alone vs. Following Nouns:
Because 'ผู้' (phûu) already means 'person', ผู้ที่ (phûu thîi) usually stands alone as a subject or object. However, in highly formal contexts, it can follow formal nouns like 'บุคคล' (bùk-khon - person), as in 'บุคคลผู้ที่...' (bùk-khon phûu thîi...). For standard everyday nouns like 'นักเรียน' (nák-rian - student), learners should just use 'ที่' (thîi) instead of 'ผู้ที่' (phûu thîi) (e.g., นักเรียนที่... nák-rian thîi...).

9. Tense and Aspect Markers:
When using tense or aspect markers, they are placed after 'ที่' (thîi) and inside the relative clause. For example, use 'ผู้ที่จะ...' (phûu thîi jà... - those who will...) or 'ผู้ที่กำลัง...' (phûu thîi gam-lang... - those who are currently...).

10. Negative Statements:
To form a negative statement, place ไม่ (mâi - not) before the predicate inside the relative clause. A future marker can come between 'ที่' (thîi) and the negative marker. For example, 'ผู้ที่ไม่...' (phûu thîi mâi... - those who do not...).

11. Distinction from Occupational Compounds:
When ผู้ (phûu) is attached directly to a noun or action without ที่ (thîi), it often acts as a prefix to form occupational titles or fixed compound nouns. For example, ผู้จัดการ (phûu jàt gaan - manager) or ผู้ชาย (phûu chaai - man). In these cases, it functions as a single noun rather than a relative clause.

12. Proverbs and Maxims:
ผู้ที่ (phûu thîi) or the shorthand ผู้ + Verb is the standard structure for maxims, idioms, and Buddhist teachings, equivalent to the English 'He who...' or 'Those who...'. For example, 'ผู้ทำดีย่อมได้ดี' (phûu tham dii yɔ̂m dâai dii - He who does good, receives good).