Oracle 18c

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CREATE TABLE yourtable (cust_dt date);
insert into yourtable values (sysdate-2);
1 rows affected

insert into yourtable values (trunc(sysdate));
1 rows affected

insert into yourtable values (trunc(sysdate)-3);
1 rows affected

insert into yourtable values (trunc(sysdate)-16);
1 rows affected

insert into yourtable values (trunc(sysdate)-32);
1 rows affected

insert into yourtable values (trunc(sysdate)-50);
1 rows affected

insert into yourtable values (trunc(sysdate)+80);
1 rows affected

SELECT cust_dt FROM yourtable 
WHERE cust_dt BETWEEN ADD_MONTHS(TRUNC(sysdate,'mm'),-1) AND 
LAST_DAY(ADD_MONTHS(TRUNC(sysdate,'mm'),-1));

CUST_DT

30-MAY-22

17-MAY-22

01-MAY-22

SELECT cust_dt FROM yourtable 
WHERE  cust_dt BETWEEN ADD_MONTHS(TRUNC(sysdate,'mm'),-1)
                   AND TRUNC(sysdate,'MM')-INTERVAL '0.001' SECOND;

CUST_DT

31-MAY-22

30-MAY-22

17-MAY-22

01-MAY-22